Composition of the (1 1 0) surface of the Fe–Ni 34 at.% alloy: a study by low-energy ion scattering

The composition of the (1 1 0) surface of the Fe–Ni 34 at.% alloy has been determined by means of low-energy ion scattering (LEIS). Since the masses of the iron and nickel nuclides are rather close, a curve fitting procedure was needed to determine the contribution of the two metals to the LEIS signal. The LEIS measurements have been performed in a temperature range between room temperature and 850 K. Shadow cone effects were exploited, measuring the LEIS spectra with the ion beam incident along appropriate azimuthal direction, in order to determine the composition of the topmost layer only. We found that the surface concentration of nickel increases for increasing temperatures. At 850 K the composition of the topmost layer is 41±2 at.% of Ni.